Low filled polypropylene composition with balanced property profile

ABSTRACT

The present invention relates to a polyolefin composition comprising (a) a heterophasic propylene copolymer, wherein the xylene cold soluble fraction of the heterophasic propylene copolymer has an intrinsic viscosity of lower than 2.0 dl/g, (b) a high density polyethylene having a density of at least 940 kg/m 3 , (c) a linear low density polyethylene, and (d) an inorganic filler, wherein the polyolefin composition has a MFR 2  (230° C.) of at least 20 g/10 min.

The present invention relates to a new polyolefin composition comprisinga heterophasic propylene copolymer (HECO), a high density polyethylene(HDPE), a second polyethylene (PE2) having a density of below 940 kg/m³,and an inorganic filler (F). The present invention also relates to anarticle comprising the said polyolefin composition, to a process for thepreparation of the polyolefin composition and to uses thereof.

Polypropylene is the material of choice in many applications as it canbe tailored to specific purposes needed. For instance heterophasicpolypropylenes are widely used in the automobile industry (for instancein bumper applications) as they combine good stiffness with reasonableimpact strength behavior. Heterophasic polypropylenes contain apolypropylene matrix in which an amorphous phase is dispersed. Theamorphous phase contains a propylene copolymer rubber, like an ethylenepropylene rubber (EPR) or an ethylene propylene diene monomer polymer(EPDM). Further the heterophasic polypropylene contains a crystallinepolyethylene to some extent. In the automobile industry suchheterophasic polypropylene grades contain an amount of about 30 wt.-%propylene copolymer rubber, which normally is produced directly in oneor two gas phase reactors or added externally to the matrix via acompounding step.

In the field of automotive exterior applications the thermal expansionof a polymer is of great importance. The coefficient of linear thermalexpansion (CLTE) determines the minimum gap width between two parts.Most of the time, the parts are made from different materials. To avoidbig gaps and high stresses in the parts, the coefficient of linearthermal expansion (CLTE) should be as low as possible.

The conventional way of reducing the coefficient of linear thermalexpansion (CLTE) in automotive compounds is to incorporate inorganicfillers (usually at high loadings, i.e. 10 to 30 wt.-%). The reductionof thermal expansion and shrinkage via filler-addition is based on twodifferent mechanisms that most of the time act simultaneously:

-   -   volume dilution with a material of lower shrinkage/CLTE    -   mechanical constraint by a dispersed phase with low CLTE and        high modulus. For this purpose fillers with high aspect ratios        are normally used.

A disadvantage of this method is that the materials may suffer from poortoughness, bad appearance and difficulties in processing. Furthermore,the weight of these parts increases through the filler incorporation. Tominimize the need for filler incorporation the polymer itself shouldfeature a high dimensional stability. Additionally the materials shouldshow high flowability and balanced mechanical properties, e.g. goodstiffness and high ductility. A high tensile strain at break is oftenthought to be an indicator of ductility. Whereas low filler loadings arebeneficial for a high tensile strain at break, high flowability isdetrimental for this property since the strain at break is decreasingbelow a critical molecular weight with increasing melt flow rate due toa lower amount of entanglements in the polymer chain.

For example, materials with a rubber of low intrinsic viscosity (IV) mayalso show a low shrinkage or thermal expansion. However, materials witha rubber of low intrinsic viscosity (IV) also typically have a lowimpact strength, which is undesired especially in the automotive field.Furthermore, since automotive parts are predominantly produced by meansof injection moulding, a high melt flow rate (MFR) is highly desirablein order to facilitate the manufacture of large injection moulded parts.

Thus, there remains a need in the art for a polyolefin compositionhaving at the same time a low coefficient of linear thermal expansion(CLTE), a high impact strength, and a high melt flow rate (MFR) atpreferably low filler content. The object of the present invention is tomeet the above need.

Further surface defects, which are also known as flow marks, tigerstripes or flow lines, are deteriorating the surface aesthetics sincethey manifest, during injection moulding, as a series of alternatinghigh and low gloss strips perpendicular to the direction of the meltflow. Accordingly it is envisaged to find a polyolefin composition whichdoes not show at all or only minor flow marks.

The present inventors have surprisingly found that a polyolefincomposition having a melt flow rate MFR₂ (230° C.) of at least 20 g/10min and comprising a heterophasic propylene copolymer (HECO), whereinthe xylene cold soluble fraction (XCS) of the heterophasic propylenecopolymer (HECO) has an intrinsic viscosity of lower than 2.0 dl/g, andfurther comprising a high density polyethylene, a second polyethylenedifferent to the high density polyethylene and an inorganic filler, cansolve the above addressed problems.

Thus, the present invention relates in a first aspect to a polyolefincomposition (PO) comprising

-   (a) a heterophasic propylene copolymer (HECO) comprising    -   (a1) a polypropylene (PP), and    -   (a2) an elastomeric propylene copolymer (E),    -   wherein the xylene cold soluble (XCS) fraction of the        heterophasic propylene copolymer (HECO) has an intrinsic        viscosity of lower than 2.0 dl/g,-   (b) a high density polyethylene (HDPE) having a density of at least    940 kg/m³,-   (c) a second polyethylene (PE2) having a density of below 940 kg/m³,    and-   (d) an inorganic filler (F),    wherein the polyolefin composition (PO) has a melt flow rate MFR₂    (230° C.) of at least 20 g/10 min.

The present invention also relates to an article, preferably anautomotive article, comprising the above polyolefin composition (PO).

The present invention further relates to a process for the preparationof the above polyolefin composition (PO) by extruding the heterophasicpropylene copolymer (HECO), the high density polyethylene (HDPE), thelinear low density polyethylene (LLDPE), and the inorganic filler (F) inan extruder.

A further aspect of the present invention is the use of the abovepolyolefin composition (PO) in an automotive application.

Further preferred embodiments of the present invention are described inthe appended claims.

In the following the invention will be described in more detail below.

The polyolefin composition (PO) of the present invention comprises in apreferred embodiment

-   (a) at least 50 wt.-%, like at least 60 wt.-%, more preferably 50 to    90 wt.-%, still more preferably 60 to 80 wt.-%, yet more preferably    65 to 75 wt.-% of the heterophasic propylene copolymer (HECO);-   (b) at least 5 wt.-%, preferably 5 to 25 wt.-%, more preferably 8 to    20 wt.-%, still more preferably 9 to 17 wt.-% of the high density    polyethylene (HDPE);-   (c) at least 5 wt.-%, preferably 5 to 25 wt.-%, more preferably 6 to    20 wt.-%, still more preferably 7 to 15 wt.-%, yet more preferably 8    to 14 wt.-% of the second polyethylene (PE2);-   (d) up to 20 wt.-%, preferably up to 10 wt.-%, more preferably 2 to    15 wt.-%, still more preferably 3 to 10 wt.-% of the inorganic    filler (F),    based on the total polyolefin composition (PO), preferably based on    the total amount of polymers present in the polyolefin composition    (PO) and the inorganic filler (F), more preferably based on the    heterophasic propylene copolymer (HECO), the high density    polyethylene (HDPE), the second polyethylene (PE2) and the inorganic    filler (F).

In a preferred embodiment, the weight ratio of the high densitypolyethylene (HDPE) to the second polyethylene (PE2) [(HDPE)/(PE2)] is2:1 to 1:4, more preferably is 1:1 to 1:3.

In a further preferred embodiment, the weight ratio of the elastomericpropylene copolymer (E) to the high density polyethylene (HDPE)[(E)/(HDPE)] is 4:1 to 1:2, more preferably is 3:1 to 1:1.

The melt flow rate MFR₂ (230° C.) of the total polyolefin composition(PO) preferably is at least 22 g/10 min, more preferably at least 25g/10 min, still more preferably is in the range of 20 to 100 g/10 min,more preferably 22 to 50 g/10 min.

The polyolefin composition of the instant invention is featured by goodmechanical properties. Accordingly it is preferred that the polyolefincomposition (PO) has tensile modulus of at least 1,000 MPa, morepreferably in the range of 1,000 to 2,200 MPa, still more preferably inthe range of 1,100 to 1,700 MPa.

Further also the impact strength should be rather high. Accordingly itis appreciated that the polyolefin composition (PO) has a Charpy notchedimpact strength (ISO 179 1eA) at 23° C. of at least 18 kJ/m², morepreferably of at least 20 kJ/m², yet more preferably in the range of 20to 70 kJ/m², still more preferably in the range of 28 to 60 kJ/m²,and/or has a Charpy notched impact strength (ISO 179 1eA) at −30° C. ofat least 1.5 kJ/m², more preferably of at least 2.5 kJ/m², yet morepreferably in the range of 2.0 to 10.0 kJ/m², still more preferably inthe range of 2.5 to 8.0 kJ/m².

The elongation at break should also be high. Accordingly, it isappreciated that the polyolefin composition (PO) has an elongation atbreak of at least 200%, preferably at least 220%, more preferably in therange of 200 to 450%, like in the range of 220 to 400%.

Furthermore, the polyolefin composition (PO) of the present inventionpreferably shows a low coefficient of linear thermal expansion (CLTE).It is preferred that the polyolefin composition (PO) has a coefficientof linear thermal expansion (CLTE) performed in a temperature range from−30 to +80° C. of not more than 100 μm/mK, more preferably of not morethan 90 μm/mK, still more preferably in the range of 60 to 90 μm/mK, yetmore preferably in the range of 65 to 85 μm/mK. These values are inparticular applicable in case the polyolefin composition (PO) comprisesnot more than 8 wt.-%, i.e. not more than 7 wt.-% inorganic filler (F),the weight percentage is measured on the total polyolefin composition(PO).

Furthermore, the polyolefin composition (PO) of the present inventionpreferably shows a low radial shrinkage. For example, the polyolefincomposition (PO) has a radial shrinkage of 2.0% or lower, morepreferably of 1.5% or lower, even more preferably in the range of 0.2 to1.5%, still more preferably in the range of 0.25 to 1.1%.

Furthermore, the polyolefin composition (PO) of the present inventionpreferably shows a very low difference in radial and tangentialshrinkage. For example, the polyolefin composition (PO) has differencein radial to tangential shrinkage of equal or below 0.1%, like in therange of 0.01 to 0.1%, the percentage is determined by the formulaST−SRwherein

-   ST is the tangential shrinkage [%].-   SR is the radial shrinkage [%]

The polyolefin composition (PO) in accordance with the present inventionmay be prepared by compounding the components within suitable meltmixing devices for preparing polymeric compounds, including inparticular extruders, like single screw extruders as well as twin screwextruders. Other suitable melt mixing devices include planet extrudersand single screw co-kneaders. Especially preferred are twin screwextruders including high intensity mixing and kneading sections.Suitable melt temperatures for preparing the compositions are in therange from 170 to 300° C., preferably in the range from 200 to 260° C.

In the following the individual components are defined in more detail.

Heterophasic Propylene Copolymer

The expression “heterophasic” as used in the instant invention indicatesthat the elastomeric propylene copolymer (E) is (finely) dispersed inthe polypropylene (PP). In other words the polypropylene (PP)constitutes a matrix in which the elastomeric propylene copolymer (E)forms inclusions in the matrix, i.e. in the polypropylene (PP). Thus thematrix contains (finely) dispersed inclusions being not part of thematrix and said inclusions contain the elastomeric propylene copolymer(E). The term “inclusion” according to this invention shall preferablyindicate that the matrix and the inclusion form different phases withinthe heterophasic system, said inclusions are for instance visible byhigh resolution microscopy, like electron microscopy or scanning forcemicroscopy.

Further it is preferred that the heterophasic propylene copolymer (HECO)before mixed with the other components mentioned herein comprises aspolymer components only the polypropylene (PP) and the elastomericpropylene copolymer (E). In other words the heterophasic propylenecopolymer (HECO) may contain further additives but no other polymer inan amount exceeding 7.5 wt-%, more preferably exceeding 5 wt.-%, basedon the total heterophasic propylene copolymer (HECO), more preferablybased on the polymers present in the propylene copolymer (HECO). Oneadditional polymer which may be present in such low amounts is apolyethylene which is a reaction product obtained by the preparation ofthe heterophasic propylene copolymer (HECO). Accordingly it is inparticular appreciated that a heterophasic propylene copolymer (HECO) asdefined in the instant invention contains only a polypropylene (PP), anelastomeric propylene copolymer (E) and optionally a polyethylene inamounts as mentioned in this paragraph.

Also the polyolefin composition (PO) of the present invention can beregarded as a heterophasic system. Accordingly the polypropylene (PP) ofthe heterophasic propylene copolymer (HECO) constitutes also the matrixof the overall polyolefin composition (PO). The elastomeric propylenecopolymer (E), the high density polyethylene (HDPE), the secondpolyethylene (PE2), and the inorganic filler (F) are (finely) dispersedin said matrix. Thereby the elastomeric propylene copolymer (E), thehigh density polyethylene (HDPE), and the second polyethylene (PE2) mayform separate inclusions in the matrix, i.e. in the polypropylene (PP),or the high density polyethylene (HDPE) and the second polyethylene(PE2), respectively, may form an inclusion within the inclusion of theelastomeric propylene copolymer (E).

The heterophasic propylene copolymer (HECO) has a melt flow rate MFR₂(230° C.) of at least 30 g/10 min, more preferably in the range of 30 to300 g/10 min, still more preferably in the range of 35 to 200 g/10 min,yet more preferably in the range of 40 to 125 10 g/10 min.

Preferably it is desired that the heterophasic propylene copolymer(HECO) is thermo mechanically stable. Accordingly it is appreciated thatthe heterophasic propylene copolymer (HECO) has a melting temperature(T_(m)) of at least 135° C., more preferably in the range of 135 to 170°C., yet more preferably in the range of 145 to 168° C.

Preferably the propylene content in the heterophasic propylene copolymer(HECO) is 75.0 to 95.0 wt.-%, more preferably 80.0 to 90.0 wt.-%, basedon the total heterophasic propylene copolymer (HECO), more preferablybased on the amount of the polymer components of the heterophasicpropylene copolymer (HECO), yet more preferably based on the amount ofthe polypropylene (PP) and the elastomeric propylene copolymer (E)together. The remaining part constitutes the comonomers as defined forthe polypropylene (PP) being a random propylene copolymer (R-PP) and theelastomeric propylene copolymer (E), respectively, preferably ethylene.Accordingly the comonomer content, preferably ethylene content, is inthe range of 5.0 to 25.0 wt.-%, more preferably in the range of 10.0 to20.0 wt.-%, based on the total heterophasic propylene copolymer (HECO),more preferably based on the amount of the polymer components of theheterophasic propylene copolymer (HECO), yet more preferably based onthe amount of the polypropylene (PP) and the elastomeric propylenecopolymer (E) together.

In a preferred embodiment, the heterophasic propylene copolymer (HECO)has a comonomer content of 7 to 20 wt.-%, more preferably 9 to 17 wt.-%,still more preferably 10 to 15 wt.-%, based on the total weight of theheterophasic propylene copolymer (HECO). The comonomers are preferablyethylene and/or a C₄ to C₁₂ olefin, especially ethylene, based on thetotal heterophasic propylene copolymer (HECO), more preferably based onthe amount of the polymer components of the heterophasic propylenecopolymer (HECO), yet more preferably based on the amount of thepolypropylene (PP) and the elastomeric propylene copolymer (E) together.

As stated above the matrix of the heterophasic propylene copolymer(HECO) is the polypropylene (PP).

The polypropylene (PP) according to this invention has preferably a meltflow rate MFR₂ (230° C.) of 40 to 200 g/10 min, preferably in the rangeof 50 to 150 g/10 min.

Accordingly it is preferred that the polypropylene (PP) has a weightaverage molecular weight (M_(w)) from 90,000 to 300,000 g/mol, morepreferably from 100,000 to 250,000 g/mol.

A broad molecular weight distribution (MWD) improves the processabilityof the polypropylene. Accordingly it is appreciated that the molecularweight distribution (MWD) of the polypropylene (PP) is at least 2.8,more preferably at least 3.0, like at least 3.3 In a preferredembodiment the molecular weight distribution (MWD) is preferably between2.8 to 10.0, still more preferably in the range of 3.0 to 8.0.

The polypropylene (PP) can be a propylene homopolymer (H-PP) or randompropylene copolymer (R-PP), the latter is preferred.

Accordingly it is appreciated that the polypropylene (PP) has acomonomer content equal or below 5.0 wt.-%, more preferably equal orbelow 3.0 wt.-%, based on the polypropylene (PP).

The expression propylene homopolymer used in the instant inventionrelates to a polypropylene that consists substantially, i.e. of morethan 99.5 wt.-%, still more preferably of at least 99.7 wt.-%, like ofat least 99.8 wt.-%, of propylene units. In a preferred embodiment onlypropylene units in the propylene homopolymer are detectable.

In case the polypropylene (PP) is a random propylene copolymer (R-PP) itcomprises monomers copolymerizable with propylene, for examplecomonomers such as ethylene and/or C₄ to C₁₂ α-olefins, in particularethylene and/or C₄ to C₁₀ α-olefins, e.g. 1-butene and/or 1-hexene.Preferably the random propylene copolymer (R-PP) comprises, especiallyconsists of, monomers copolymerizable with propylene from the groupconsisting of ethylene, 1-butene and 1-hexene. More specifically therandom propylene copolymer (R-PP) comprises—apart from propylene—unitsderivable from ethylene and/or 1-butene. In a preferred embodiment therandom propylene copolymer (R-PP) comprises units derivable fromethylene and propylene only. The comonomer content in the randompropylene copolymer (R-PP) is preferably in the range of more than 0.5to 5.0 wt.-%, still more preferably in the range of more than 0.5 to 3.0wt.-%, based on the random propylene copolymer (R-PP).

The term “random copolymer” indicates that the comonomers within thepropylene copolymer (PP) are randomly distributed. The randomnessdefines the amount of isolated comonomer units, i.e. those which have noneighbouring comonomer units, compared to the total amount of comonomersin the polymer chain.

The polypropylene (PP) can have a xylene cold soluble content (XCS) inthe range up to 6.0 wt.-%. Accordingly the polypropylene (PP) may have axylene cold soluble content (XCS) in the range of 0.5 to 4.5 wt.-%,based on the polypropylene (PP).

The polypropylene (PP) can be produced in different reactors and thusmay comprises different fractions being different in its properties. Forinstance the fractions may differ in melt flow rate or comonomercontent, the latter being preferred. Accordingly in one preferredembodiment the polypropylene (PP) is a random propylene copolymer (R-PP)comprising at least two fractions. More preferably the random propylenecopolymer (R-PP) comprises, more preferably consists of, a first polymerfraction being either a propylene homopolymer fraction or a randompropylene propylene copolymer fraction and a second polymer fractionbeing a random propylene copolymer fraction. In such a case it ispreferred that the weight ratio of the first fraction to the secondfraction is 30:70 to 70:30. Preferably the first polymer fraction is apropylene homopolymer fraction whereas the second fraction is apropylene copolymer fraction with a comonomer content, like ethylenecontent, of not more than 3.0 wt.-%, more preferably in the range of 0.5to 3.0 wt.-%, like 0.5 to 2.0 wt.-%, based on the second fraction.

One further essential component of the heterophasic propylene copolymer(HECO) is its elastomeric propylene copolymer (E).

The elastomeric propylene copolymer (E) preferably comprises monomerscopolymerizable with propylene, for example comonomers such as ethyleneand/or C₄ to C₁₂ α-olefins, in particular ethylene and/or C₄ to C₁₀α-olefins, e.g. 1-butene and/or 1-hexene. Preferably the elastomericpropylene copolymer (E) comprises, especially consists of, monomerscopolymerizable with propylene from the group consisting of ethylene,1-butene and 1-hexene. More specifically the elastomeric propylenecopolymer (E) comprises—apart from propylene—units derivable fromethylene and/or 1-butene. Thus in an especially preferred embodiment theelastomeric propylene copolymer phase (E) comprises units derivable fromethylene and propylene only.

In case the polypropylene (PP) is a random propylene copolymer (R-PP) itis preferred that the comonomer(s) of the random propylene copolymer(R-PP) and the elastomeric propylene copolymer (E) are the same.

The properties of the elastomeric propylene copolymer phase (E) mainlyinfluence the xylene cold soluble (XCS) content of the heterophasicpropylene copolymer (HECO). Thus according to the present invention thexylene cold soluble (XCS) fraction of heterophasic propylene copolymer(HECO) is regarded as the elastomeric propylene copolymer (E) of theheterophasic propylene copolymer (HECO). In the context of the presentinvention, the xylene cold soluble (XCS) fraction is also referred to as“amorphous fraction”.

Accordingly, the amount of the elastomeric propylene copolymer (E), i.e.of the xylene cold soluble (XCS) fraction, of the heterophasic propylenecopolymer (HECO) is preferably at least 10.0 wt.-%, more preferably isin the range of 10.0 to 35.0 wt.-%, still more preferably in the rangeof 12.0 to 30.0 wt.-%, yet more preferably in the range of 15.0 to 25.0wt.-%. These values are based on the heterophasic propylene copolymer(HECO) and not on the polyolefin composition (PO).

Low intrinsic viscosity (IV) values reflect a low weight averagemolecular weight. Thus it is appreciated that the elastomeric propylenecopolymer phase (E), i.e. the xylene cold soluble fraction (XCS) of theheterophasic propylene copolymer (HECO), has an intrinsic viscosity (IV)of lower than 2.2 dl/g, preferably of 2.0 dl/g or lower, more preferablyof 1.8 or lower, such as in the range of 1.0 to lower than 2.0 dl/g,preferably in the range of equal or more than 1.2 to equal or less than1.8 dl/g.

The comonomer content, preferably the ethylene content, within theelastomeric propylene copolymer phase (E) shall be preferably also in aspecific range. Accordingly in a preferred embodiment the comonomercontent, more preferably ethylene content, of the elastomeric propylenecopolymer (E), i.e. of the xylene cold soluble fraction (XCS) of theheterophasic propylene copolymer (HECO), is equal or more than 30.0wt.-%, more preferably in the range of 30.0 to 70.0 wt.-%, still morepreferably in the range of 35.0 to 55.0 wt.-%, based on the xylene coldsoluble fraction (XCS) of the heterophasic propylene copolymer (HECO).Accordingly it is appreciated that the propylene content of theelastomeric propylene copolymer (E), i.e. of the xylene cold solublefraction (XCS) of the heterophasic propylene copolymer (HECO), is lessthan 70.0 wt.-%, more preferably in the range of 30.0 to 70.0 wt.-%,still more preferably in the range of 45.0 to 65.0 wt.-%, based on thexylene cold soluble fraction (XCS) of the heterophasic propylenecopolymer (HECO).

In a preferred embodiment, the elastomeric propylene copolymer (E) isbimodal or multimodal. More particularly, the elastomeric propylenecopolymer (E) preferably is bimodal or multimodal in view of theintrinsic viscosity and/or the comonomer distribution.

Accordingly the elastomeric propylene copolymer (E) may comprise atleast two fractions of different comonomer content and/or of differentintrinsic viscosity (IV).

Thus in a specific embodiment, elastomeric propylene copolymer (E)comprises, preferably consists of, a fraction (A) and a fraction (B),said fraction (A) has a lower comonomer content and/or a differentintrinsic viscosity than fraction (B).

Fraction (A) may be an elastomeric propylene copolymer (E1) having acomonomer content, like etylene content, of 35.0 to 80.0 wt.-%, morepreferably of 40.0 to 70.0 wt.-%, based on the fraction (A) and/or anintrinsic viscosity of 1.0 to 2.0 dl/g, more preferably of 1.2 to 1.8dl/g, still more preferably of 1.2 to 1.6 dl/g. Furthermore, fraction(B) may be an elastomeric propylene copolymer (E2) having a comonomercontent, like ethylene content, of 10.0 to 35.0 wt.-%, more preferablyof 10.0 to 30.0 wt.-%, based on fraction (B) and/or an intrinsicviscosity of 1.2 to 2.5 dl/g, more preferably of 1.5 to 2.3 dl/g.Although the provided ranges for the comonomer content and intrinsicviscosity, respectively, for fraction (A) and (B), i.e. for theelastomeric propylene copolymer (E1) and the elastomeric propylenecopolymer (E2), overlapp, this does not mean that they are identical.Accordingly it is preferred that the comonomer content, like ethylenecontent, of fraction (A), i.e. of elastomeric propylene copolymer (E1),is at least 5.0 wt.-% higher than of fraction (B), i.e. of elastomericpropylene copolymer (E2), and/or the intrinsic viscosity of fraction(A), i.e. of elastomeric propylene copolymer (E1), is at least 0.2 dl/glower than the intrinsic viscosity of fraction (B), i.e. of elastomericpropylene copolymer (E2).

As will be explained below, the heterophasic polypropylene (HECO) aswell their individual components (matrix and elastomeric copolymer) canbe produced by blending different polymer types, i.e. of differentmolecular weight and/or comonomer content. However it is preferred thatthe heterophasic polypropylene (HECO) as well their individualcomponents (matrix and elastomeric copolymer) are produced in asequential step process, using reactors in serial configuration andoperating at different reaction conditions. As a consequence, eachfraction prepared in a specific reactor will have its own molecularweight distribution and/or comonomer content distribution.

The heterophasic propylene copolymer (HECO) according to this inventionis preferably produced in a sequential polymerization process, i.e. in amultistage process, known in the art, wherein the polypropylene (PP) isproduced at least in one slurry reactor, preferably in a slurry reactorand optionally in a subsequent gas phase reactor, and subsequently theelastomeric propylene copolymer (E) is produced at least in one, i.e.one or two, gas phase reactor(s).

Accordingly it is preferred that the heterophasic propylene copolymer(HECO) is produced in a sequential polymerization process comprising thesteps of

-   (a) polymerizing propylene and optionally at least one ethylene    and/or C₄ to C₁₂ α-olefin in a first reactor (R1) obtaining the    first polymer fraction, preferably said first polymer fraction is a    propylene homopolymer,-   (b) transferring the first polymer fraction into a second reactor    (R2), like a gas phase reactor,-   (c) polymerizing in the second reactor (R2) and in the presence of    said first polymer fraction propylene and optionally at least one    ethylene and/or C₄ to C₁₂ α-olefin obtaining thereby the second    polymer fraction, preferably said second polymer fraction is a    random propylene copolymer fraction, said first polymer fraction and    said second polymer fraction form the polypropylene (PP), i.e. the    matrix of the heterophasic propylene copolymer (HECO),-   (d) transferring the polypropylene (PP) of step (c) into a third    reactor (R3),-   (e) polymerizing in the third reactor (R3) and in the presence of    the polypropylene (PP) obtained in step (c) propylene and at least    one ethylene and/or C₄ to C₁₂ α-olefin obtaining thereby a first    elastomeric propylene copolymer (E1), the first elastomeric    propylene copolymer (E1) is dispersed in the polypropylene (PP),-   (f) transferring the polypropylene (PP) in which the first    elastomeric propylene copolymer (E1) is dispersed in a fourth    reactor (R4), and-   (g) polymerizing in the fourth reactor (R4) and in the presence of    the mixture obtained in step (e) propylene and at least one ethylene    and/or C₄ to C₁₂ α-olefin obtaining thereby the second elastomeric    propylene copolymer (E2),-    the polypropylene (PP), the first elastomeric propylene copolymer    (E1), and the second elastomeric propylene copolymer (E2) form the    heterophasic propylene copolymer (HECO).

Of course, in the first reactor (R1) the second polypropylene fractioncan be produced and in the second reactor (R2) the first polypropylenefraction can be obtained. The same holds true for the elastomericpropylene copolymer phase. Accordingly in the third reactor (R3) thesecond elastomeric propylene copolymer fraction can be produced whereasin the fourth reactor (R4) the first elastomeric propylene copolymerfraction is made.

Preferably between the second reactor (R2) and the third reactor (R3)and optionally between the third reactor (R3) and fourth reactor (R4)the monomers are flashed out.

The term “sequential polymerization process” indicates that theheterophasic propylene copolymer (HECO) is produced in at least two,like three or four reactors connected in series. Accordingly the presentprocess comprises at least a first reactor (R1) and a second reactor(R2), more preferably a first reactor (R1), a second reactor (R2), athird reactor (R3) and a fourth reactor (R4). The term “polymerizationreactor” shall indicate that the main polymerization takes place. Thusin case the process consists of four polymerization reactors, thisdefinition does not exclude the option that the overall processcomprises for instance a pre-polymerization step in a pre-polymerizationreactor. The term “consist of” is only a closing formulation in view ofthe main polymerization reactors.

The first reactor (R1) is preferably a slurry reactor (SR) and can beany continuous or simple stirred batch tank reactor or loop reactoroperating in bulk or slurry. Bulk means a polymerization in a reactionmedium that comprises of at least 60% (w/w) monomer. According to thepresent invention the slurry reactor (SR) is preferably a (bulk) loopreactor (LR).

The second reactor (R2), the third reactor (R3) and the fourth reactor(R4) are preferably gas phase reactors (GPR). Such gas phase reactors(GPR) can be any mechanically mixed or fluid bed reactors. Preferablythe gas phase reactors (GPR) comprise a mechanically agitated fluid bedreactor with gas velocities of at least 0.2 m/sec. Thus it isappreciated that the gas phase reactor is a fluidized bed type reactorpreferably with a mechanical stirrer.

Thus in a preferred embodiment the first reactor (R1) is a slurryreactor (SR), like a loop reactor (LR), whereas the second reactor (R2),the third reactor (R3) and the fourth reactor (R4) are gas phasereactors (GPR). Accordingly for the instant process at least four,preferably four polymerization reactors, namely a slurry reactor (SR),like a loop reactor (LR), a first gas phase reactor (GPR-1), a secondgas phase reactor (GPR-2) and a third gas phase reactor (GPR-3)connected in series are used. If needed prior to the slurry reactor (SR)a pre-polymerization reactor is placed.

A preferred multistage process is a “loop-gas phase”-process, such asdeveloped by Borealis A/S, Denmark (known as BORSTAR® technology)described e.g. in patent literature, such as in EP 0 887 379, WO92/12182 WO 2004/000899, WO 2004/111095, WO 99/24478, WO 99/24479 or inWO 00/68315.

A further suitable slurry-gas phase process is the Spheripol® process ofBasell.

Preferably, in the instant process for producing the heterophasicpropylene copolymer (HECO) as defined above the conditions for the firstreactor (R1), i.e. the slurry reactor (SR), like a loop reactor (LR), ofstep (a) may be as follows:

-   -   the temperature is within the range of 50° C. to 110° C.,        preferably between 60° C. and 100° C., more preferably between        68 and 95° C.,    -   the pressure is within the range of 20 bar to 80 bar, preferably        between 40 bar to 70 bar,    -   hydrogen can be added for controlling the molar mass in a manner        known per se.

Subsequently, the reaction mixture from step (a) is transferred to thesecond reactor (R2), i.e. gas phase reactor (GPR-1), i.e. to step (c),whereby the conditions in step (c) are preferably as follows:

-   -   the temperature is within the range of 50° C. to 130° C.,        preferably between 60° C. and 100° C.,    -   the pressure is within the range of 5 bar to 50 bar, preferably        between 15 bar to 35 bar,    -   hydrogen can be added for controlling the molar mass in a manner        known per se.

The condition in the third reactor (R3) and the fourth reactor (R4),preferably in the second gas phase reactor (GPR-2) and third gas phasereactor (GPR-3), is similar to the second reactor (R2).

The residence time can vary in the three reactor zones.

In one embodiment of the process for producing the polypropylene theresidence time in bulk reactor, e.g. loop is in the range 0.1 to 2.5hours, e.g. 0.15 to 1.5 hours and the residence time in gas phasereactor will generally be 0.2 to 6.0 hours, like 0.5 to 4.0 hours.

If desired, the polymerization may be effected in a known manner undersupercritical conditions in the first reactor (R1), i.e. in the slurryreactor (SR), like in the loop reactor (LR), and/or as a condensed modein the gas phase reactors (GPR).

Preferably the process comprises also a prepolymerization with thecatalyst system, as described in detail below, comprising aZiegler-Natta procatalyst, an external donor and optionally acocatalyst.

In a preferred embodiment, the prepolymerization is conducted as bulkslurry polymerization in liquid propylene, i.e. the liquid phase mainlycomprises propylene, with minor amount of other reactants and optionallyinert components dissolved therein.

The prepolymerization reaction is typically conducted at a temperatureof 10 to 60° C., preferably from 15 to 50° C., and more preferably from20 to 45° C.

The pressure in the prepolymerization reactor is not critical but mustbe sufficiently high to maintain the reaction mixture in liquid phase.Thus, the pressure may be from 20 to 100 bar, for example 30 to 70 bar.

The catalyst components are preferably all introduced to theprepolymerization step. However, where the solid catalyst component (i)and the cocatalyst (ii) can be fed separately it is possible that only apart of the cocatalyst is introduced into the prepolymerization stageand the remaining part into subsequent polymerization stages. Also insuch cases it is necessary to introduce so much cocatalyst into theprepolymerization stage that a sufficient polymerization reaction isobtained therein.

It is possible to add other components also to the prepolymerizationstage. Thus, hydrogen may be added into the prepolymerization stage tocontrol the molecular weight of the prepolymer as is known in the art.Further, antistatic additive may be used to prevent the particles fromadhering to each other or to the walls of the reactor.

The precise control of the prepolymerization conditions and reactionparameters is within the skill of the art.

According to the invention the heterophasic propylene copolymer (HECO)is obtained by a multistage polymerization process, as described above,in the presence of a catalyst system comprising as component (i) aZiegler-Natta procatalyst which contains a transesterification productof a lower alcohol and a phthalic ester.

The procatalyst used according to the invention is prepared by

a) reacting a spray crystallized or emulsion solidified adduct of MgCl₂and a C₁-C₂ alcohol with TiCl₄

b) reacting the product of stage a) with a dialkylphthalate of formula(I)

-   -   wherein R^(1′) and R^(2′) are independently at least a C₅ alkyl        under conditions where a transesterification between said C₁ to        C₂ alcohol and said dialkylphthalate of formula (I) takes place        to form the internal donor

c) washing the product of stage b) or

d) optionally reacting the product of step c) with additional TiCl₄

The procatalyst is produced as defined for example in the patentapplications WO 87/07620, WO 92/19653, WO 92/19658 and EP 0 491 566. Thecontent of these documents is herein included by reference.

First an adduct of MgCl₂ and a C₁-C₂ alcohol of the formula MgCl₂*nROH,wherein R is methyl or ethyl and n is 1 to 6, is formed. Ethanol ispreferably used as alcohol.

The adduct, which is first melted and then spray crystallized oremulsion solidified, is used as catalyst carrier.

In the next step the spray crystallized or emulsion solidified adduct ofthe formula MgCl₂*nROH, wherein R is methyl or ethyl, preferably ethyland n is 1 to 6, is contacting with TiCl₄ to form a titanized carrier,followed by the steps of

-   -   adding to said titanised carrier        -   (i) a dialkylphthalate of formula (I) with R^(1′) and R^(2′)            being independently at least a C₅-alkyl, like at least a            C₈-alkyl,        -   or preferably        -   (ii) a dialkylphthalate of formula (I) with R^(1′) and            R^(2′) being the same and being at least a C₅-alkyl, like at            least a C₈-alkyl,        -   or more preferably        -   (iii) a dialkylphthalate of formula (I) selected from the            group consisting of propylhexylphthalate (PrHP),            dioctylphthalate (DOP), di-iso-decylphthalate (DIDP), and            ditridecylphthalate (DTDP), yet more preferably the            dialkylphthalate of formula (I) is a dioctylphthalate (DOP),            like di-iso-octylphthalate or diethylhexylphthalate, in            particular diethylhexylphthalate,    -   to form a first product,    -   subjecting said first product to suitable transesterification        conditions, i.e. to a temperature above 100° C., preferably        between 100 to 150° C., more preferably between 130 to 150° C.,        such that said methanol or ethanol is transesterified with said        ester groups of said dialkylphthalate of formula (I) to form        preferably at least 80 mol-%, more preferably 90 mol-%, most        preferably 95 mol.-%, of a dialkylphthalate of formula (II)

-   -   with R¹ and R² being methyl or ethyl, preferably ethyl, the        dialkylphthalat of formula (II) being the internal donor and    -   recovering said transesterification product as the procatalyst        composition (component (i)).

The adduct of the formula MgCl₂*nROH, wherein R is methyl or ethyl and nis 1 to 6, is in a preferred embodiment melted and then the melt ispreferably injected by a gas into a cooled solvent or a cooled gas,whereby the adduct is crystallized into a morphologically advantageousform, as for example described in WO 87/07620.

This crystallized adduct is preferably used as the catalyst carrier andreacted to the procatalyst useful in the present invention as describedin WO 92/19658 and WO 92/19653.

As the catalyst residue is removed by extracting, an adduct of thetitanised carrier and the internal donor is obtained, in which the groupderiving from the ester alcohol has changed.

In case sufficient titanium remains on the carrier, it will act as anactive element of the procatalyst.

Otherwise the titanization is repeated after the above treatment inorder to ensure a sufficient titanium concentration and thus activity.

Preferably the procatalyst used according to the invention contains 2.5wt.-% of titanium at the most, preferably 2.2% wt.-% at the most andmore preferably 2.0 wt.-% at the most. Its donor content is preferablybetween 4 to 12 wt.-% and more preferably between 6 and 10 wt.-%.

More preferably the procatalyst used according to the invention has beenproduced by using ethanol as the alcohol and dioctylphthalate (DOP) asdialkylphthalate of formula (I), yielding diethyl phthalate (DEP) as theinternal donor compound.

Still more preferably the catalyst used according to the invention isthe BCF20P catalyst of Borealis (prepared according to WO 92/19653 asdisclosed in WO 99/24479; especially with the use of dioctylphthalate asdialkylphthalate of formula (I) according to WO 92/19658) or thecatalyst Polytrack 8502, commercially available from Grace.

For the production of the heterophasic propylene copolymer (HECO)according to the invention the catalyst system used preferably comprisesin addition to the special Ziegler-Natta procatalyst an organometalliccocatalyst as component (ii).

Accordingly it is preferred to select the cocatalyst from the groupconsisting of trialkylaluminium, like triethylaluminium (TEA), dialkylaluminium chloride and alkyl aluminium sesquichloride.

Component (iii) of the catalysts system used is an external donorrepresented by formula (IIIa) or (IIIb). Formula (IIIa) is defined bySi(OCH₃)₂R₂ ⁵  (IIIa)wherein R⁵ represents a branched-alkyl group having 3 to 12 carbonatoms, preferably a branched-alkyl group having 3 to 6 carbon atoms, ora cyclo-alkyl having 4 to 12 carbon atoms, preferably a cyclo-alkylhaving 5 to 8 carbon atoms.

It is in particular preferred that R⁵ is selected from the groupconsisting of iso-propyl, iso-butyl, iso-pentyl, tert.-butyl,tert.-amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl andcycloheptyl.

Formula (IIIb) is defined bySi(OCH₂CH₃)₃(NR^(x)R^(y))  (IIIb)wherein R^(x) and R^(y) can be the same or different a represent ahydrocarbon group having 1 to 12 carbon atoms.

R^(x) and R^(y) are independently selected from the group consisting oflinear aliphatic hydrocarbon group having 1 to 12 carbon atoms, branchedaliphatic hydrocarbon group having 1 to 12 carbon atoms and cyclicaliphatic hydrocarbon group having 1 to 12 carbon atoms. It is inparticular preferred that R^(x) and R^(y) are independently selectedfrom the group consisting of methyl, ethyl, n-propyl, n-butyl, octyl,decanyl, iso-propyl, iso-butyl, iso-pentyl, tert.-butyl, tert.-amyl,neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl.

More preferably both R^(x) and R^(y) are the same, yet more preferablyboth R^(x) and R^(y) are an ethyl group.

More preferably the external donor of formula (IIIb) isdiethylaminotriethoxysilane.

Most preferably the external donor is of formula (IIIa), likedicyclopentyl dimethoxy silane [Si(OCH₃)₂(cyclo-pentyl)₂] or diisopropyldimethoxy silane [Si(OCH₃)₂(CH(CH₃)₂)₂].

In a further embodiment, the Ziegler-Natta procatalyst can be modifiedby polymerizing a vinyl compound in the presence of the catalyst system,comprising the special Ziegler-Natta procatalyst (component (i)), anexternal donor (component (iii) and optionally a cocatalyst (component(iii)), which vinyl compound has the formula:CH₂═CH—CHR³R⁴wherein R³ and R⁴ together form a 5- or 6-membered saturated,unsaturated or aromatic ring or independently represent an alkyl groupcomprising 1 to 4 carbon atoms, and the modified catalyst is used forthe preparation of the heterophasic propylene copolymer according tothis invention. The polymerized vinyl compound can act as anα-nucleating agent.

Concerning the modification of catalyst reference is made to theinternational applications WO 99/24478, WO 99/24479 and particularly WO00/68315, incorporated herein by reference with respect to the reactionconditions concerning the modification of the catalyst as well as withrespect to the polymerization reaction.

Accordingly it is appreciated that the heterophasic propylene copolymer(HECO) is α-nucleated. In case the α-nucleation is not effected by avinylcycloalkane polymer or a vinylalkane polymer as indicated above,the following α-nucleating agents (N) may be present

-   (i) salts of monocarboxylic acids and polycarboxylic acids, e.g.    sodium benzoate or aluminum tert-butylbenzoate, and-   (ii) dibenzylidenesorbitol (e.g. 1,3:2,4 dibenzylidenesorbitol) and    C₁-C₈-alkyl-substituted dibenzylidenesorbitol derivatives, such as    methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or    dimethyldibenzylidenesorbitol (e.g. 1,3:2,4    di(methylbenzylidene)sorbitol), or substituted nonitol-derivatives,    such as    1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol,    and-   (iii) salts of diesters of phosphoric acid, e.g. sodium    2,2′-methylenebis (4,6,-di-tert-butylphenyl)phosphate or    aluminium-hydroxy-bis[2,2′-methylene-bis(4,6-di-t-butylphenyl)phosphate],    and-   (iv) mixtures thereof.    High Density Polyethylene (HDPE)

The polyolefin composition according to the present invention furthercomprises a high density polyethylene (HDPE). The high densitypolyethylene (HDPE) used according to the invention is well known in theart and commercially available.

The a high density polyethylene (HDPE) preferably has a melt flow rateMFR₂ (190° C.) of 0.4 to 4.0 g/10 min, preferably 0.5 to 2.0 g/10 min,more preferably of 0.6 to 1.5 g/10 min, like 0.7 to 1.4 g/10 min.

The high density polyethylene (HDPE) typically has a density of at least940 kg/m³, preferably of at least 945 kg/m³, more preferably at least955 kg/m³, still more preferably in the range of 945 to 970 kg/m³, yetmore preferably in the range of 950 to 965 kg/m³.

As mentioned above, the high density polyethylene (HDPE) is alsodispersed in the matrix, i.e. in the polypropylene (PP), of theheterophasic propylene copolymer (HECO) and thus forming the overallpolyolefin composition (PO).

Second Polyethylene (PE2)

As mentioned above, the instant polyolefin composition (PO) comprisesfurther a second polyethylene (PE2). The second polyethylene (PE2) usedaccording to the invention is well known in the art and commerciallyavailable.

The second polyethylene (PE2) has a lower density than the high densitypolyethylene (HDPE).

Accordingly, the second polyethylene (PE2) is a polyethylene with a lowdensity, i.e. preferably having a density of below 940 kg/m³, morepreferably 920 kg/m³ or lower, yet more preferably in the range of 800to 915 kg/m³, still more preferably in the range of 840 to 910 kg/m³. Insome embodiments, the second polyethylene (PE2) is a low densitypolyethylene and/or a linear low density polyethylene (LLDPE).Preferably the second polyethylene (PE2) is a linear low densitypolyethylene (LLDPE).

A low density polyethylene (LDPE) according to this invention preferablyhas a density of 900 to below 940 kg/m³, more preferably of 910 to below940 kg/m³, like 910 to 935 kg/m³.

On the other hand the linear low density polyethylene (LLDPE) accordingto this invention has a density of below 900 kg/m³, more preferably of800 to below 900 kg/m³, yet more preferably of 820 to below 900 kg/m³,still yet more preferably 820 to below 890 kg/m³.

In a preferred embodiment, the second polyethylene (PE2), i.e. thelinear low density polyethylene (LLDPE), has a melt flow rate MFR₂ (190°C.) in the range of 0.5 to 30 g/10 min, more preferably in the range of0.5 to below 15 g/10 min, yet more preferably in the range of 1 to 10g/10 min.

In case the second polyethylene (PE2) is a low density polyethylene(LDPE) it can be an ethylene homopolymer or an ethylene copolymer, thelatter being preferred. Accordingly the ethylene content in the lowdensity polyethylene (LDPE) is at least 80 wt.-%, more preferably atleast 90 wt.-%, based on the low density polyethylene (LDPE).

The expression ethylene homopolymer used in the instant inventionrelates to a polyethylene that consists substantially, i.e. of more than99.7 wt.-%, still more preferably of at least 99.8 wt.-%, of ethyleneunits. In a preferred embodiment only ethylene units in the ethylenehomopolymer are detectable.

In case the second polyethylene (PE2) is a linear low densitypolyethylene (LLDPE) it is preferably an ethylene copolymer thatcontains as a major part units derivable from ethylene. Accordingly itis appreciated that the linear low density polyethylene (LLDPE)comprises at least 55 wt.-% units derivable from ethylene, morepreferably at least 60 wt.-% of units derived from ethylene, based onthe linear low density polyethylene (LLDPE). Thus it is appreciated thatthe linear low density polyethylene (LLDPE) comprises units derivablefrom ethylene in the range of 60 to 99.5 wt.-%, more preferably in therange of 60 to 80 wt.-%, on linear low density polyethylene (LLDPE). Thecomonomers present in such a second polyethylene (PE2), i.e. the linearlow density polyethylene (LLDPE), are C₄ to C₂₀ α-olefins, like1-butene, 1-hexene and 1-octene, the latter especially preferred, ordienes, preferably non-conjugated α,ω-alkadienes, i.e. C₅ to C₂₀α,ω-alkadienes, like 1,7-octadiene. Accordingly in one specificembodiment the second polyethylene (PE2), i.e. the linear low densitypolyethylene (LLDPE), being an ethylene copolymer is anethylene-1,7-octadiene polymer with the amounts given in this paragraph.

The second polyethylene (PE2) preferably is also dispersed in thematrix, i.e. in the polypropylene (PP), of the heterophasic propylenecopolymer (HECO) and thus forming the overall polyolefin composition(PO).

Inorganic Filler

In addition to the polymer components the polyolefin composition (PO)comprises an inorganic filler (F) in amounts of up to 20 wt.-%,preferably in an amount of up to 10 wt.-%, more preferably in the rangeof 4 to 15 wt.-%, still more preferably 5 to 10 wt.-%. Preferably theinorganic filler (F) is a phyllosilicate, mica or wollastonite. Evenmore preferred the inorganic filler (F) is selected from the groupconsisting of mica, wollastonite, kaolinite, smectite, montmorilloniteand talc. The most preferred the inorganic filler (F) is talc.

The mineral filler (F) preferably has a cutoff particle size d95 [masspercent] of equal or below 20 μm, more preferably in the range of 2.5 to10 μm, like in the range of 2.5 to 8.0 μm.

Typically the inorganic filler (F) has a surface area measured accordingto the commonly known BET method with N₂ gas as analysis adsorptive ofless than 22 m²/g, more preferably of less than 20 m²/g, yet morepreferably of less than 18 m²/g. Inorganic fillers (F) fulfilling theserequirements are preferably anisotropic mineral fillers (F), like talc,mica and wollastonite.

Further Components

The instant polyolefin composition (PO) may comprise typical additives,like acid scavengers (AS), antioxidants (AO), nucleating agents (NA),hindered amine light stabilizers (HALS), slip agents (SA), and pigments.Preferably the amount of additives excluding the inorganic filler (F)shall not exceed 7 wt.-%, more preferably shall not exceed 5 wt.-%, likenot more than 3 wt.-%, within the instant polyolefin composition (PO).

Articles Made from the Polyolefin Composition (PO)

The polyolefin composition (PO) of the present invention is preferablyused for the production of automotive articles, like moulded automotivearticles, preferably automotive injection moulded articles. Even morepreferred is the use for the production of car interiors and exteriors,like bumpers, side trims, step assists, body panels, spoilers,dashboards, interior trims and the like, especially bumpers.

The current invention also provides (automotive) articles, likeinjection molded articles, comprising at least to 60 wt.-%, morepreferably at least 80 wt.-%, yet more preferably at least 95 wt.-%,like consisting, of the inventive polyolefin composition (PO).Accordingly the present invention is especially directed to automotivearticles, especially to car interiors and exteriors, like bumpers, sidetrims, step assists, body panels, spoilers, dashboards, interior trimsand the like, in particular bumpers, comprising at least to 60 wt.-%,more preferably at least 80 wt.-%, yet more preferably at least 95wt.-%, like consisting, of the inventive polyolefin composition (PO).

Uses According to the Invention

The present invention also relates to the use of the polyolefincomposition (PO) as described above in an automotive application. In apreferred embodiment, the polyolefin composition (PO) is used in abumper.

The present invention will now be described in further detail by theexamples provided below.

EXAMPLES

The following definitions of terms and determination methods apply forthe above general description of the invention as well as to the belowexamples unless otherwise defined.

1. Definitions/Measuring Methods

The following definitions of terms and determination methods apply forthe above general description of the invention as well as to the belowexamples unless otherwise defined.

Melting temperature (T_(m)) and heat of fusion (H_(f)), crystallizationtemperature (T_(c)) and heat of crystallization (H_(c)): measured withMettler TA820 differential scanning calorimetry (DSC) on 5 to 10 mgsamples. DSC is run according to ISO 3146/part 3/method C2 in aheat/cool/heat cycle with a scan rate of 10° C./min in the temperaturerange of +23 to +210° C. Crystallization temperature and heat ofcrystallization (H_(c)) are determined from the cooling step, whilemelting temperature and heat of fusion (H_(f)) are determined from thesecond heating step

Density is measured according to ISO 1183-1—method A (2004). Samplepreparation is done by compression moulding in accordance with ISO1872-2:2007.

MFR₂ (230° C.) is measured according to ISO 1133 (230° C., 2.16 kgload).

Calculation of melt flow rate MFR₂ (230° C.) of the polymer produced inthe GPR 1:

${{MFR}\left( {P\; 2} \right)} = 10^{\lbrack\frac{{\log{({{MFR}{(P)}})}} - {{w{({P\; 1})}} \times {\log{({{MFR}{({P\; 1})}})}}}}{w{({P\; 2})}}\rbrack}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the polymer produced in    the loop reactor,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR 1,-   MFR(P1) is the melt flow rate MFR₂ (230° C.) [in g/10 min] of the    polymer produced in the loop reactor,-   MFR(P) is the total melt flow rate MFR₂ (230° C.) [in g/10 min]    after GPR₁ but before GPR2,-   MFR(P2) is the calculated melt flow rate MFR₂ (230° C.) [in g/10    min] of the polymer produced in the GPR 1.

MFR₂ (190° C.) is measured according to ISO 1133 (190° C., 2.16 kgload).

Number average molecular weight (M_(n)), weight average molecular weight(M_(w)) and molecular weight distribution (MWD) are determined by GelPermeation Chromatography (GPC) according to the following method:

The weight average molecular weight Mw and the molecular weightdistribution (MWD=Mw/Mn wherein Mn is the number average molecularweight and Mw is the weight average molecular weight) is measured by amethod based on ISO 16014-1:2003 and ISO 16014-4:2003. A Waters AllianceGPCV 2000 instrument, equipped with refractive index detector and onlineviscosimeter was used with 3×TSK-gel columns (GMHXL-HT) from TosoHaasand 1,2,4-trichlorobenzene (TCB, stabilized with 200 mg/L 2,6-Di tertbutyl-4-methyl-phenol) as solvent at 145° C. and at a constant flow rateof 1 mL/min. 216.5 μL of sample solution were injected per analysis. Thecolumn set was calibrated using relative calibration with 19 narrow MWDpolystyrene (PS) standards in the range of 0.5 kg/mol to 11 500 kg/moland a set of well characterized broad polypropylene standards. Allsamples were prepared by dissolving 5-10 mg of polymer in 10 mL (at 160°C.) of stabilized TCB (same as mobile phase) and keeping for 3 hourswith continuous shaking prior sampling in into the GPC instrument.

Quantification of Comonomer Content by FTIR Spectroscopy

The comonomer content is determined by quantitative Fourier transforminfrared spectroscopy (FTIR) after basic assignment calibrated viaquantitative ¹³C nuclear magnetic resonance (NMR) spectroscopy in amanner well known in the art. Thin films are pressed to a thickness ofbetween 100-500 μm and spectra recorded in transmission mode.Specifically, the ethylene content of a polypropylene-co-ethylenecopolymer is determined using the baseline corrected peak area of thequantitative bands found at 720-722 and 730-733 cm⁻¹. Specifically, thebutene or hexene content of a polyethylene copolymer is determined usingthe baseline corrected peak area of the quantitative bands found at1377-1379 cm⁻¹. Quantitative results are obtained based upon referenceto the film thickness. Calculation of comonomer content of the polymerproduced in the GPR 1:

$\frac{{C(P)} - {{w\left( {P\; 1} \right)} \times {C\left( {P\; 1} \right)}}}{w\left( {P\; 2} \right)} = {C\left( {P\; 2} \right)}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the polymer produced in    the loop reactor,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR1,-   C(P1) is the comonomer content [in wt.-%] of the polymer produced in    the loop reactor,-   C(P) is the total comonomer content [in wt.-%] after GPR1 but before    GPR2,-   C(P2) is the calculated comonomer content [in wt.-%] of the polymer    produced in the GPR1.

Calculation of comonomer content of the polymer produced in the GPR 2:

$\frac{{C(P)} - {{w\left( {P\; 1} \right)} \times {C\left( {P\; 1} \right)}}}{w\left( {P\; 2} \right)} = {C\left( {P\; 2} \right)}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the total polymer in the    GPR1,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR2,-   C(P1) is the comonomer content [in wt.-%] in the GPR1,-   C(P) is the total comonomer content [in wt.-%] after GPR2 but before    GPR3,-   C(P2) is the calculated comonomer content [in wt.-%] of the polymer    produced in the GPR2.

Calculation of comonomer content of the polymer produced in the GPR 3:

$\frac{{C(P)} - {{w\left( {P\; 1} \right)} \times {C\left( {P\; 1} \right)}}}{w\left( {P\; 2} \right)} = {C\left( {P\; 2} \right)}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the total polymer in the    GPR2,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR3,-   C(P1) is the comonomer content [in wt.-%] in the GPR2,-   C(P) is the total comonomer content [in wt.-%] after GPR3,-   C(P2) is the calculated comonomer content [in wt.-%] of the polymer    produced in the GPR3.

The xylene cold solubles (XCS, wt.-%): Content of xylene cold solubles(XCS) is determined at 25° C. according ISO 16152; first edition; 2005Jul. 1

Calculation of the xylene cold soluble (XCS) content of the polymerproduced in the GPR 1:

$\frac{{{XS}(P)} - {{w\left( {P\; 1} \right)} \times {{XS}\left( {P\; 1} \right)}}}{w\left( {P\; 2} \right)} = {{XS}\left( {P\; 2} \right)}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the polymer produced in    the loop reactor,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR1,-   XS(P1) is the xylene cold soluble (XCS) content [in wt.-%] of the    polymer produced in the loop reactor,-   XS(P) is the total xylene cold soluble (XCS) content [in wt.-%]    after GPR1 but before GPR2,-   XS(P2) is the calculated xylene cold soluble (XCS) content [in    wt.-%] of the polymer produced in the GPR1.

Calculation of the xylene cold soluble (XCS) content of the polymerproduced in the GPR 2:

$\frac{{{XS}(P)} - {{w\left( {P\; 1} \right)} \times {{XS}\left( {P\; 1} \right)}}}{w\left( {P\; 2} \right)} = {{XS}\left( {P\; 2} \right)}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the total polymer in    GPR1,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR2,-   XS(P1) is the xylene cold soluble (XCS) content [in wt.-%] of the    total polymer in GPR1,-   XS(P) is the total xylene cold soluble (XCS) content [in wt.-%]    after GPR2 but before GPR3,-   XS(P2) is the calculated xylene cold soluble (XCS) content [in    wt.-%] of the polymer produced in the GPR2.

Calculation of the xylene cold soluble (XCS) content of the polymerproduced in the GPR 3:

$\frac{{{XS}(P)} - {{w\left( {P\; 1} \right)} \times {{XS}\left( {P\; 1} \right)}}}{w\left( {P\; 2} \right)} = {{XS}\left( {P\; 2} \right)}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the total polymer in    GPR2,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR3,-   XS(P1) is the xylene cold soluble (XCS) content [in wt.-%] of the    total polymer in GPR2,-   XS(P) is the total xylene cold soluble (XCS) content [in wt.-%]    after GPR3,-   XS(P2) is the calculated xylene cold soluble (XCS) content [in    wt.-%] of the polymer produced in the GPR3.

Intrinsic viscosity is measured according to DIN ISO 1628/1, October1999 (in Decalin at 135° C.).

Calculation of the intrinsic viscosity of the polymer produced in theGPR 2:

${{IV}\left( {P\; 2} \right)} = 10^{\lbrack\frac{{\log{({{IV}{(P)}})}} - {{w{({P\; 1})}} \times {\log{({{IV}{({P\; 1})}})}}}}{w{({P\; 2})}}\rbrack}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the total polymer in the    GPR1,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR 2,-   IV(P1) is the intrinsic viscosity [in dl/g] of the total polymer in    GPR1,-   IV(P) is the total intrinsic viscosity [in dl/g] after GPR2 but    before GPR3,-   IV(P2) is the calculated intrinsic viscosity [in dl/g] of the    polymer produced in the GPR 2.

Calculation of the intrinsic viscosity of the polymer produced in theGPR 3:

${{IV}\left( {P\; 2} \right)} = 10^{\lbrack\frac{{\log{({{IV}{(P)}})}} - {{w{({P\; 1})}} \times {\log{({{IV}{({P\; 1})}})}}}}{w{({P\; 2})}}\rbrack}$wherein

-   w(P1) is the weight fraction [in wt.-%] of the total polymer in the    GPR2,-   w(P2) is the weight fraction [in wt.-%] of the polymer produced in    the GPR 3,-   IV(P1) is the intrinsic viscosity [in dl/g] of the total polymer in    GPR2,-   IV(P) is the total intrinsic viscosity [in dl/g] after GPR3,-   IV(P2) is the calculated intrinsic viscosity [in dl/g] of the    polymer produced in the GPR 3.

The tensile modulus, the tensile strength, the tensile stress at yield,the strain at yield and the elongation at break is measured at 23° C.according to ISO 527-1 (cross head speed 1 mm/min) using injectionmoulded specimens according to ISO 527-2(1B), produced according to ENISO 1873-2 (dog 10 bone shape, 4 mm thickness).

Coefficient of linear thermal expansion: The coefficient of linearthermal expansion (CLTE) was determined in accordance with ISO11359-2:1999 on 10 mm long pieces cut from the same injection moldedspecimens as used for the flexural modulus determination. Themeasurement was performed in a temperature range from −30 to +80° C. ata heating rate of 1° C./min.

Charpy impact test: The Charpy notched impact strength (Charpy NIS) ismeasured according to ISO 179 1eA at 23° C., −30° C., using injectionmolded bar test specimens of 80×10×4 mm prepared in accordance with ISO294-1:1996.

Cutoff particle size d95 (Sedimentation) is calculated from the particlesize distribution [mass percent] as determined by gravitational liquidsedimentation according to ISO 13317-3 (Sedigraph)

Specific surface area is determined as the BET surface according to DIN66131/2.

Shrinkage is determined on centre gated, injection moulded circulardisks (diameter 180 mm, thickness 3 mm, having a flow angle of 355° anda cut out of 5°). Two specimens are moulded applying two differentholding pressure times (10 s and 20 s respectively). The melttemperature at the gate is 260° C., and the average flow front velocityin the mould 100 mm/s Tool temperature: 40° C., back pressure: 600 bar.

After conditioning the specimen at room temperature for 96 hours thedimensional changes radial and tangential to the flow direction aremeasured for both disks. The average of respective values from bothdisks are reported as final results.

Flow Marks

The tendency to show flow marks was examined with a method as describedbelow. This method is described in detail in WO 2010/149529, which isincorporated herein in its entirety.

An optical measurement system, as described by Sybille Frank et al. inPPS 25 Intern. Conf. Polym. Proc. Soc 2009 or Proceedings of the SPIE,Volume 6831, pp 68130T-68130T-8 (2008) was used for characterizing thesurface quality.

This method consists of two aspects:

1. Image Recording.

The basic principle of the measurement system is to illuminate theplates with a defined light source (LED) in a closed environment and torecord an image with a CCD-camera system. A schematic setup is given inFIG. 1.

2. Image Analysis:

The specimen is floodlit from one side and the upwards reflected portionof the light is deflected via two mirrors to a CCD-sensor. The suchcreated grey value image is analyzed in lines. From the recordeddeviations of grey values the mean square error (MSE) is calculatedallowing a quantification of surface quality, i.e. the larger the MSEvalue the more pronounced is the surface defect.

Generally, for one and the same material, the tendency to flow marksincreases when the injection speed is increased.

For this evaluation plaques 210×148×3 mm³ with grain VW K50 and afilmgate of 1.4 mm were used and were produced with two differentinjection speeds using screw speeds of 1 mm/sec (MSE 1) and 8 mm/sec(MSE 5).

Further Conditions:

Melt temperature: 240° C.

Mould temperature 30° C.

Dynamic pressure: 10 bar hydraulic

The smaller the MSE value is at a certain injection speed, the smalleris the tendency for flow marks.

2. Examples

An experimental heterophasic propylene copolymer (HECO) was produced ina Borstar pilot plant with a prepolymerization reactor, one slurry loopreactor and three gas phase reactors using a Ziegler-Natta catalyst. Thecatalyst used in the polymerization process for inventive examples IE1and IE2 was the commercial BCF20P catalyst (1.9 wt %Ti-Ziegler-Natta-catalyst as described in EP 591 224) of Borealis AGwith triethyl-aluminium (TEAL) as cocatalyst and dicyclo pentyldimethoxy silane (D-donor) as donor. The preparation of the heterophasicpropylene copolymer (HECO) including the aluminium to donor ratio isdescribed in the following table 1.

TABLE 1 Preparation of the heterophasic propylene copolymer (HECO)Catalyst TEAL/Donor [mol/mol] 5 Loop MFR₂ [g/10 min] 68 XCS [wt %] 2.8C₂ [wt %] 0.0 1^(st) GPR MFR₂ [g/10 min] 65 MFR₂* [g/10 min] 62 XCS [wt%] 2.2 XCS* [wt %] 1.6 C₂ [wt %] 1.0 C₂* [wt %] 2.0 2^(nd) GPR XCS [wt%] 13.3 C₂ tot [wt %] 10.9 C₂ of XCS** [wt %] 60 C₂ of XCS [wt %] 60 IVof XCS** [dl/g] 1.4 IV of XCS [dl/g] 1.4 3^(rd) GPR H₂/C₂ [mol/kmol] 500C₂/C₃ [mol/kmol] 310 MFR₂ [g/10 min] 44 XCS [wt %] 18.7 C₂ of XCS*** [wt%] 24.5 C₂ of XCS [wt %] 49 IV of XCS*** [dl/g] 2.15 IV of XCS [dl/g]1.6 Tm [° C. ] 162 Split Loop/GPR1/GPR2/GPR3 [wt %] 42/42/11/5 *polymerproduced in GPR 1 **XCS produced in GPR2, which can be equated with thepolymer produced in GPR2 ***XCS produced in GPR3, which can be equatedwith the polymer produced in GPR3

TABLE 2 Inventive and Comparative Examples Example* IE 1 IE 2 CE 1 HECO[wt %] 68 70 Talc [wt %] 6 6 HDPE [wt %] 15 10 PE2 [wt %] 8 11 MFR [g/10min] 25 26 12 Tensile Modulus [MPa] 1290 1190 1200 Elongation at break[%] 240 305 300 Impact strength +23° C. [kJ/m²] 30 42 35 Impact strength−30° C. [kJ/m²] 4 4 4.5 CLTE (−30/80) [μm/mK] 77 73 70 Shrinkage radial% 1.08 1.0 0.95 Shrinkage tangential % 1.1 1.07 0.90 MSE 1 [—] 4 91 MSE5 [—] 3 11 Rest to 100 wt.-% are additives, like antioxidants andpigments (e.g. Carbon black) “Talc” is the commercial talc Steamic T1 CAof Luzenac, having a cutoff particle size (d₉₅) of 6.2 μm. “HDPE” is thecommercial productVS5580 of Borealis AG having a MFR₂ (190° C./2.16 kg)of 0.95 g/10 min and a density of 958 kg/m³, “PE2” is the commerciallinear low density polyethylene (LLDPE) Engage 8200 of Dow Elastomershaving a MFR₂ (190° C./2.16 kg) of 5.0 g/10 min, a density of 870 kg/m³.“CE1” is the commercial product Borcom WE007AE of Borealis AG which is apolypropylene microcomposite intended for injection moulding having amineral filler content of 4.5 wt. %.

The inventive examples IE1 and to IE2 show a high flowability, a highelongation at break, and a radial shrinkage of only about 1%. Thetensile modulus is about 1200 MPa or higher and the room temperatureimpact strength is about 30 kJ/m² or higher. Thus this material can beused as a high flow bumper grade. Compared to the actual commercialreference CE1 it shows similar mechanical properties and dimensionalstability at a double as high flowability.

The invention claimed is:
 1. A polyolefin composition (PO) comprising:(a) a heterophasic propylene copolymer (HECO) comprising: (a1) apolypropylene (PP), and (a2) an elastomeric propylene copolymer (E),wherein the xylene cold soluble (XCS) fraction of the heterophasicpropylene copolymer (HECO) has an intrinsic viscosity of lower than 2.0dl/g measured according to DIN ISO 1628/1 (in Decalin at 135° C.), (b) ahigh density polyethylene (HDPE) having a density of at least 940 kg/m³measured according to ISO 1183-1-method A, (c) a second polyethylene(PE2) having a density of below 940 kg/m³ measured according to ISO1183-1-method A which is (i) a low density polyethylene (LDPE), or (ii)a linear low density polyethylene (LLDPE), (d) an inorganic filler (F),wherein the polyolefin composition (PO) has a melt flow rate MFR₂ (230°C.) of at least 20 g/10 min measured according to ISO 1133 (230° C.,2.16 kg load).
 2. The polyolefin composition (PO) according to claim 1,wherein the heterophasic propylene copolymer (HECO): (a) has a melt flowrate MFR₂ (230° C.) in the range of 30 to 100 g/10 min measuredaccording to ISO 1133 (230° C., 2.16 kg load), and/or (b) comprises theelastomeric propylene copolymer (E) in an amount of 10 to 35 wt. %,and/or (c) is comprised in the polyolefin composition in an amount of 50to 90 wt. % based on the total weight of the polyolefin composition(PO), and/or (d) has a comonomer content of 5.0 to 25.0 wt. % based onthe total weight of the heterophasic propylene copolymer (HECO).
 3. Thepolyolefin composition (PO) according to claim 1, wherein elastomericpropylene copolymer (E) (a) is bimodal or multimodal, and/or (b) has anintrinsic viscosity (IV) of lower than 2.0 dl/g, measured as theintrinsic viscosity (IV) of the xylene cold soluble (XCS) fraction ofthe heterophasic propylene copolymer (HECO) according to DIN ISO 1628/1(in Decalin at 135° C.), and/or (c) has a comonomer content of 30 to 70wt. % based on the total weight of the xylene cold soluble (XCS)fraction of the heterophasic propylene copolymer (HECO).
 4. Thepolyolefin composition (PO) according to claim 1, wherein: (a) theweight ratio [(HDPE)/(PE2)] of the high density polyethylene (HDPE) tothe second polyethylene (PE2) is 2:1 to 1:4; and/or (b) the weight ratio[(E)/(HDPE)] of the elastomeric propylene copolymer (E) to the highdensity polyethylene (HDPE) is 4:1 to 1:2; and/or (c) the polyolefincomposition (PO) comprises the high density polyethylene (HDPE) in anamount of 5 to 25 wt. %; and/or (d) the polyolefin composition (PO)comprises the second polyethylene (PE2) in an amount of 5 to 25 wt. %.5. The polyolefin composition (PO) according to claim 1, wherein thepolypropylene (PP) is a random propylene copolymer (R-PP).
 6. Thepolyolefin composition according to claim 1, wherein the polyolefincomposition (PO) comprises the inorganic filler (F) in an amount of upto 20 wt. % based on the total weight of the polyolefin composition(PO).
 7. The polyolefin composition (PO) according to claim 6, whereinthe inorganic filler (F) has a cutoff particle size d95 [mass percent]of equal or below 20 μm measured according to 13317-3 (Sedigraph). 8.The polyolefin composition (PO) according to claim 1, wherein the highdensity polyethylene (HDPE) has a density of at least 945 kg/m³ measuredaccording to ISO 1183-1-method A.
 9. The polyolefin composition (PO)according to claim 1, wherein the second polyethylene (PE2): (a) has amelt flow rate MFR₂ (190° C.) in the range of 0.5 to 30 g/10 minmeasured according to ISO 1133 (190° C., 2.16 kg load), and/or (b) is anethylene copolymer.
 10. The polyolefin composition (PO) according toclaim 1 provided in an article.
 11. The polyolefin composition accordingto claim 10, wherein the article is an automotive article.
 12. Thepolyolefin composition (PO) according to claim 11, wherein theautomotive article is a bumper.